No abstract

The residual defects and groups in chemically reduced graphene oxide cannot only improve the impedance match characteristic and prompt energy transition from contiguous states to Fermi level, but also introduce defect polarization relaxation and groups’ electronic dipole relaxation, which are all in favor of electromagnetic wave penetration and absorption. The chemically reduced graphene oxide shows enhanced microwave absorption compared with graphite and carbon nanotubes, and can be expected to display better absorption than high quality graphene, exhibiting a promising prospect as microwave absorbing material.

A fundamental and persistent problem in the study of carbonbased electrode materials for lithium ion batteries is the question of how many lithium ions can be inserted onto a C 6 aromatic ring. Although different empirical models of Li x /C 6 (x < 3) have been proposed, the question remains unresolved. Herein we employ 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), an aromatic compound containing a naphthalene ring system (fused C 6 aromatic rings), to demonstrate that each carbon in a C 6 ring can accept a Li ion to form a Li 6 /C 6 additive complex through a reversible electrochemical lithium addition reaction. This process results in Li ion insertion capacities of up to nearly 2000 mA h g À1 , depending on the exact molecular structure. This value is several times higher than any other organic electrode material previously reported and can be fully released under certain conditions. Our experiments and theoretical calculations indicate that the anhydride groups on the sides of the aromatic system are crucial for this process, which provides a promising strategy for the design of novel high-performance organic electrode materials.Organic molecules [1] are intriguing candidates for electrode materials for use in rechargeable Li ion batteries. [2][3][4] The application of such species has aroused much interest recently, owing to the obvious advantages of such a system: no need for rare metals, low safety risks compared to transition metal oxides, and design flexibility at the molecular level. [5][6][7][8] However, organic molecules are usually considered to possess relatively poor specific energies and cycling properties, as compared to those of inorganic materials, and these factors greatly limit their practical application. Recently, studies on aromatic carbonyl derivatives [9,10] showed that organic materials can possess outstanding electrochemical performance comparable to, or even superior to, inorganic materials. [9,11,12] Furthermore, the wide diversity of organic redox systems, [1] as well as the excellent flexibility in their molecular design, suggest even greater prospects for these materials, and this has inspired the exploration of new organic Li ion insertion systems with improved performance.Aromatic C 6 rings are the basic structural units of graphite and other carbon-based electrode materials, which are the most commonly used anodes in commercial Li ion batteries owing to their high electric conductivity and low cost. [13][14][15] It has traditionally been believed that each C 6 ring can accept one Li ion to form an intercalated Li/C 6 complex, giving a relatively low theoretical capacity of 372 mA h g À1 . Recently, studies on graphene, [16][17][18] nanographene, [19,20] and their derivatives reveal that, through the reduction of size and dimensionality, these materials exhibit unique electric and electrochemical properties superior to those of conventional graphitic materials; thus, these materials are currently a hot research topic. In studies of electrode materials for Li ion batterie...

The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction is crucial to a variety of important energy conversion and storage processes. Here, we use carbon quantum dots (CQDs, ∼5 nm) to form hybrids with the ultrathin nickel-iron layered double-hydroxide (NiFe-LDH) nanoplates. The resulting CQD/NiFe-LDH complex exhibits high electrocatalytic activity (with an overpotential of ∼235 mV in 1 M KOH at a current density of 10 mA cm(-2)) and stability for oxygen evolution, which almost exceed the values of all previously reported Ni-Fe compounds and were comparable to those of the most active perovskite-based catalyst.

No abstract

Surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4′-dimercaptoazobenzene (DMAB) have been investigated by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O2 (as an electron acceptor) is essential and H2O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H2O (or H2) acts as the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. This SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions.

Plasmonic nanomaterials coupled with catalytically active surfaces can provide unique opportunities for various catalysis applications, where surface plasmons produced upon proper light excitation can be adopted to drive and/or facilitate various chemical reactions. A brief introduction to the localized surface plasmon resonance and recent design and fabrication of highly efficient plasmonic nanostructures, including plasmonic metal nanostructures and metal/semiconductor heterostructures is given. Taking advantage of these plasmonic nanostructures, the following highlights summarize recent advances in plasmon‐driven photochemical reactions (coupling reactions, O2 dissociation and oxidation reactions, H2 dissociation and hydrogenation reactions, N2 fixation and NH3 decomposition, and CO2 reduction) and plasmon‐enhanced electrocatalytic reactions (hydrogen evolution reaction, oxygen reduction reaction, oxygen evolution reaction, alcohol oxidation reaction, and CO2 reduction). Theoretical and experimental approaches for understanding the underlying mechanism of surface plasmon are discussed. A proper discussion and perspective of the remaining challenges and future opportunities for plasmonic nanomaterials and plasmon‐related chemistry in the field of energy conversion and storage is given in conclusion.

Microstructured Ni/PPy (PPy: polypyrrole) core/shell composites were prepared from an in situ chemical oxidative polymerization of pyrrole (Py) monomer in the presence of Ni powder, with ammonium persulfate (APS) as oxidant and citric acid (C6H8O7) as dopant. X-ray diffraction and Fourier transform infrared analyses indicate that there is no chemical interaction between Ni powder and protonated PPy. The mass percentages of PPy, calculated from the remanent weight percentages of Ni/PPy composites after thermogravimetric analysis, are in consistent with those as designed. The prepared Ni/PPy composites are soft and ferromagnetic materials, where a linear increase of saturation magnetization (MS) and remanent magnetization (MR) as a function of Ni powder content is proposed. The permeability of Ni/PPy composites presents a natural magnetic resonance at 6.0 GHz, and Cole-Cole semicircle was applied to explain the permittivity. Electromagnetic absorption less than -10 dB is found for Ni/Py=4:1 (11-15.4 GHz) and Ni/Py=2:1 (12-17.5 GHz). The ternary Debye relaxations for enhanced dielectric loss induced by PPy coatings and proper electromagnetic impedance matching due to the synergetic consequence of the Ni cores and PPy shells contribute to the improvement of the electromagnetic absorption of the Ni/PPy core/shell composites. It is important to notice that dielectric loss and electrical conductivity should be considered simultaneously in designing dielectric-type electromagnetic absorbing materials.